regulator: max77686: zero-initialize regulator match table

The struct of_regulator_match is declared as a non-static local variable
so the structure members are not auto-initialized.

Initialize the struct at declaration time to avoid the structure members
values to be indeterminate and have sane defaults instead.

Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Mark Brown <broonie@kernel.org>